Conventionally, a network device connecting servers and networks implements a spanning tree protocol (STP) for blocking one link as a technique of avoiding a layer 2 (L2) loop. Moreover, for network monitoring, a technique of displaying the STP blocking state on a control terminal is also usually used.
As a technique of monitoring a transmission speed of a network, a transmission speed of a single link connected between devices is monitored as a transmission speed between two devices connected directly. For example, a management information base (MIB) is acquired regularly, using a command such as ifspeed, from each of the devices at both ends of the single link as a monitoring target, and a transmission speed described in the acquired MIB is monitored.
Moreover, to monitor a logical network, there is also known a technique of displaying a plurality of kinds of logical network configurations for each object constituting a network, based on network configuration information collected from each of the objects. A conventional example is described in Japanese Laid-open Patent Publication No. 10-294731.
However, the conventional technique has a problem in that when a network in which a plurality of L2 switches are connected through a multipath is monitored, only a part of path of the multipath is monitored.
Recently, a large-scale network such as a data center has been constructed with a multipath (L2MP) using a technique of transparent interconnection of lots of links (TRILL), and other schemes. In this case, hosts are connected through a plurality of active paths, and the transmission and reception of data is performed using a shortest route with the least number of hops among the active routes.
When such a network with L2MP connection is monitored using the conventional technique, the conventional technique only allows monitoring of a route between two adjacent nodes, or one route, as a route connected in series, even when routes between two adjacent nodes are connected in parallel. Thus, the information of a plurality of paths altogether is not monitored. That is, the conventional technique only allows monitoring of information of one route among routes used actually, although hosts connected through L2 switches are connected via the paths.